"Thanks Steve. I don't know what 'capacitor input type' means, sorry. There are PS filter caps for each channel, but I've never looked inside the chassis."
No problem Rich. You provided me with some info.
"Could there be something wrong with the amp that makes it harm rectifier tubes? They don't have bias or any other settings besides mains input, right? Smoothing filter caps are only 1400uF per side so should not pose a problem on startup. Can playing the amp too loud damage rectifier or are they usually overrated as with bridge types?"
"It could well be that all three bad rectifiers just had something wrong with them. None were new and only the RCA was a decent brand."
That could be. I take it that is the total capacitance, 1400uf. I wonder what the value is for the first capacitor? The value of the first capacitor is important as it, along with the choke input, is responsible for the intial peak surge current upon turn on. Sometimes, the second cap is as well if the supply has multiple chokes.
What is causing the arc is either the peak hot switching current is being exceeded upon power on. Could be all the rectifiers are bad if purchased used. Some designs are tough on rectifiers.
That design appears to be an unusual as I have never heard of that high of capacitance power supply using tube rectifiers, unless most of the capacitance is for the smaller signal stages down the line. Might want to try some other rectifiers, or contact the manufacturer on this one.
Another idea, does it have a slow startup circuit? This gradually raises the voltage, limiting the transient peak current.
"Thanks for any ideas.
Rich"
Your Welcome.
